Noninvasive neuromodulation technologies that affect neuronal activity can modulate neural activity and potentially alter behavior, cognitive states, perception, and motor output without requiring an invasive procedure. To date, the majority of transdermal non-invasive neuromodulatory devices apply electrical energy to a subject's skin using one or more electrodes that typically attach to the neurostimulator via a cord or cable, which can be long and awkward to wear, particularly in a non-clinical or non-research setting.
For example, transcranial/transdermal electric stimulation (hereinafter “TES”) using scalp electrodes has been used to affect brain function in humans in the form of transcranial alternating current stimulation (hereinafter “tACS”), transcranial direct current stimulation (hereinafter “tDCS”), cranial electrotherapy stimulation (hereinafter “CES”), and transcranial random noise stimulation (hereinafter “tRNS”). Systems and methods for TES have been disclosed (see for example, Capel U.S. Pat. No. 4,646,744; Haimovich et al. U.S. Pat. No. 5,540,736; Besio et al. U.S. Pat. No. 8,190,248; Hagedorn and Thompson U.S. Pat. No. 8,239,030; Bikson et al. U.S. Patent Application Publication No. 2011/0144716; and Lebedev et al. U.S. Patent Application Publication No. 2009/0177243). tDCS systems with numerous electrodes and a high level of configurability have been disclosed (see for example Bikson et al. U.S. Patent Application Publication Nos. 2012/0209346, 2012/0265261, and 2012/0245653).
TES has been used therapeutically in various clinical applications, including treatment of pain, depression, epilepsy, and tinnitus. Despite the research to date on TES neuromodulation, existing systems and methods for delivering TES are lacking. In particular, neurostimulators that are effective, comfortable and easy-to-use, e.g., easy to apply and remove, particularly in a non-clinical (e.g., home) setting, have been lacking.
Although a handful of small, lightweight and presumably wearable neuromodulation devices have been described, none of these systems are adapted for use with electrodes (e.g., disposable electrode assemblies) for applying energy to a user's head. In particular, none of these systems may be secured to a separate electrode assembly so that the neurostimulator may be well-secured to the user's head (or other body region) for a variety of sizes of users. For example, previously described neurostimulators either attach directly to the user (e.g., adhesively, and must therefore rest directly against the user's body) or they are secured to an electrode which is secured to the body but requires additional support (e.g., from a strap or additional adhesive on the neurostimulator) to be worn by the subject.
Thus, there is a need for lightweight, wearable neuromodulation devices (e.g., neurostimulators) that may be securely worn by the user by attachment through a separate electrode assembly. Furthermore, there is a need for lightweight neurostimulators that mechanically and electrically secure to an electrode assembly in a manner that fits a variety of body shapes and sizes. In particular, there is a need for wearable neurostimulators that are configured to be comfortably wearable and will not fall off when a user is moving around, or even when a user is wearing additional clothing or glasses.
Moreover, during a TES session, capacitance might be built up between the electrodes, which might cause pain and discomfort. The user might be distracted, thus the cognitive effects of the TES might be reduced. Alternatively, the user might be sufficiently uncomfortable from the skin sensations of electrical stimulation that the subjective experience of pain overwhelms another cognitive, subjective, or physiological effect. Therefore, there is a need for a neurostimulator to include stimulation circuits that may reduce discomfort. For example, described herein are neurostimulators that include a “short-circuiting” feature that is configured to reduce discomfort and accordingly increase the cognitive effects induced by TES (due to one or both of: reducing the distraction of discomfort so that other cognitive effects can be experienced by a subject and permitting higher peak current intensities to be delivered that induce more significant cognitive effects).
In addition, there is a need for neurostimulator devices (and indeed, generally for electrical stimulation devices) that are both energy efficient and effective. In particular, there is a need for electrical stimulation devices (such as neurostimulators) that include a relatively high-voltage power source, yet that are capable of dynamically adjusting the power supplied to the electronics of the device so that power is conserved (and heat dissipation is minimized), while maintaining the functionality of the device.
Described herein are methods and apparatuses (e.g., devices and systems, and methods of operating such apparatuses) that may address at least the needs identified above.